In Sql server query window, execute query that selects all stored procedures with the prefix you want (such as procedures that start with 'cust'):
SELECT 'DROP PROCEDURE ' + Name FROM sys.objects
WHERE
type in (N'P', N'PC')
and
name like 'cust_%'
Right-click the query window and set results to text. This gives you a results window with a single column of drop prodecures. Select all the text, copy to a new query window and execute.